1. Field of the Invention
The present invention relates to RF coaxial cable connectors and more particularly to a coaxial cable connector having improved voltage standing wave ratio through minimal impedance mismatch.
2. Brief Description of Earlier Developments
In most coaxial connector designs, it is a common practice to either crimp or solder the center conductor of the cable before assembling the center contact inside the connector. Crimping the center contact is a desirable termination method due to the lower applied cost of the cable assembly. Examples of crimping an electrical terminal to an exposed end of an inner conductor of a coaxial cable can be found in U.S. Pat. Nos. 5,273,458 and 5,490,801. In these cases, the center contact of the connector is terminated to the coaxial cable conductor via a crimping tool before assembly within the outer conductor and the dielectric member. However, in connector designs that incorporate a center contact pre-assembled with the remainder of the connector, termination must be made through portals in the outer conductor shell of the assembly. Termination of the center conductor of the coaxial cable in these designs can also be either crimp or solder. Methods of crimping through portals are described in U.S. Pat. Nos. 3,297,978, 4,047,788, 4,096,627. However, portal style crimps described to date have worse RF performance levels, due to the impedance mismatch effects of the portals. U.S. Pat. Nos. 3,297,978; 4,047,788; 4,096,627 describe the crimping of the center contact of the connector through opposed crimp portals, but fail to address the resulting electrical effects of the crimped connector. With the increased need for higher frequency ranges to support for example the expanding wireless communications markets, RF connectors used in telecommunication systems are required to operate at higher frequency ranges and with lower losses to make these systems function at their peak performance. Therefore, it would be desirable to be able to connect a coaxial cable conductor to a conductor receiving member via portals in the outer conductor shell of the connector, while at the same time optimizing the impedance of the connector as well as enhancing the overall RF performance of the connector, which are results not achieved or realized using any of the conventional connectors.
The present invention is directed to in a first aspect, an electrical connector member for a coaxial cable. In one embodiment, the connector member comprises a first section and a second section. The first section has two or more portals therein, each portal adapted to guide an indentor of a crimping tool into a predetermined position over a crimp area of an electrical contact in the member. The second section includes a conductor receiving section of the electrical contact, the conductor receiving section having a diameter adapted to receive a center conductor of the cable. Each crimp area is located on the conductor receiving section, wherein an electrical connection is formed by crimping the electrical contact to the conductor at each crimp area using the indentors. The crimped connection provides a substantially matched impedance in that section of the connector.
In another aspect, the present invention is directed to an electrical connector member for a coaxial cable. In one embodiment, the member comprises a first section having four portals and a second section including a conductor receiving section of an electrical contact in an interior section of the connector. Each portal is adapted to align a corresponding indentor of a crimping tool over a predetermined crimp area on the electrical contact. Each indentor is aligned adjacent to its respective portal as the connector member is inserted into the positioner of the crimping tool. The conductor receiving section has a diameter adapted to accommodate a center conductor of the cable. Preferably, the contact is adapted to be assembled in the connector member before a crimping operation. In the preferred embodiment, the crimp on each crimp area forms an electrical connection between the contact and the conductor and provides a substantially matched impedance for the crimp section of the connector.
In another aspect, the present invention is directed to a method of making a crimp-style coaxial electrical connector assembly having a generally uniform impedance. In one embodiment, the method comprises providing a coaxial electrical connector having an inner conductor, an outer conductor and a dielectric element separating the inner and outer conductor. A coaxial cable with a center conductor is provided and the inner conductor is engaged with the center conductor. The inner conductor is crimped to the center conductor through at least two openings in the outer conductor. The crimping step creates an area of impedance mismatch on the connector that is compensated for to provide the generally uniform impedance across the connector.
In a further aspect, the present invention is directed to a coaxial electrical connector with an inner conductor crimped to a center conductor of a coaxial cable through an outer conductor. In one embodiment, the improvement comprises the outer conductor having an inner diameter selected to compensate for an impedance mismatch created by the crimp, so that the connector has a generally uniform impedance thereacross.